Mechanical timer



Nov. 8, 1966 N. F. GREEN MECHANICAL TIMER Filed March 18, 1965 INVENTOR NORMAN F. GREEN ATTORNEY Patented Nov. 8, 1966 3,283,591 MECHANICAL TIIVIER Norman F. Green, Minneapolis, Minn., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed Mar. 18, 1965, Ser. No. 440,793 Claims. (Cl. 74-3.5)

This invention relates generally to the art of timing devices and specifically concerns the design of a mechanical timing device in which the timing rate is determined by the speed at which air can escape from a permea-ble sack to which a collapsing force is being applied.

Various mechanical, electrical and chemical timing devices have -been devised for use in the countless systems in which it is necessary to provide a means for establishing a certain period of time between the occurrence of t-wo events. The present invention, a mechanical timing device, is primarily useful in those applications that require a non-reuseable, one-shot timer. Most systems in which timing devices are used require that the timing device be reSettable. For those applications, the usual clock escapement mechanism or liuid dash pot type of system may be applicable. In many systems, however, it is only necessary that the timing action be performed one time. A good example of such a system is the fuze for a g-un fired projectile. In munition fuzing, it is common -practice to incorporate a timing device to assure that the fuze does not arm until the projectile has reached a safe distance from the launch position. The present invention is a one-shot timer that could successfully be incorporated into such a system.

It is therefore an object of the present invention to provide a mechanical timing device that utilizes the rate of air flow through a permeable material in the form of a sealed, air filled sack as the time base.

A further object of the present invention is to provide a timing device that can be designed to provide a time period as short as a few seconds or as long as several days.

A still further object of the present invention is to provide a timing device that utilizes a minimum num-ber of moving parts, none of which are intricate or inherently difficult to manufacture, install or adjust.

Another object of the present invention is to provide a mechanical timing device in which a spring loaded piston moves through a chamber against an air filled sack, the `walls of which are formed from a permeable material through which the flow of air is restricted, the time base 'being established Iby the time required for Ithe piston to completely move through the chamber.

These and other objects of the invention will become apparent from the Ifollowing specification and claims, and from the accompanying drawing, wherein:

FIGURE 1 is a sectional, side view of the preferred embodiment of the timing device in the non-actuated position.

FIGURE 2 is a similar sectional view showing the timing device after actuation.

The cross-sectional side view of the timing device illustrated in FIGURE l discloses all of t-he elements of the invent-ion. The timing device includes a tubular housing member having a first end 12 and a second end 14. Housing member 10 is disclosed as being a right circular cylinder in the preferred embodiment ibut this is not critical to the invention. Formed longitudinally through the center of housing member 10 is an elongated cylindrical chamber or bore 16 that opens to each end 12 and 14. Bore 16 has a circular cross-section in the preferred embodiment but this could be changed without departing from the invention.

To close off the open ends of chamber 16, a pair of end plates 18 and 20 are attached to first end 12 and to second end 14 of housing member 10 respectively. In the preferred embodiment, end plates 18 and 20 are fitted into correspondingly sized recesses formed in the ends of housing member 10. Ends 12 and 14 are then crimped over end plates 18 and 20 as clearly shown at 22. A closed right circular cylindrical chamber results.

Mounted within chamber 16 is a :piston member 24. Piston 'member 24 is cylindrical in shape and has an out,-y side diameter that closely corresponds to the inside diameter of chamber 16. Broadly speaking, the lateral dimensions of piston member 24 would generally correspond to the lateral dimensions of chamber 16. In the preferred embodiment, piston member 24 is hollow and has a closed end 26 and an open end 2S. Piston member 24 is movable longitudinally in chamber 16 from a first position adjacent end 12 to a second position adjacent end 14.

A support member 30 is firmly attached to the center of end plate 18 and extends into the center of piston member 24 through open end 28. Mounted firmly on the end of support member 30 opposite end plate 18 is a circular plate 32. Circular plate 32 is thus immovable with respect to housing member 10 and has a diameter that closely corres-ponds to the inner diameter of the central opening in piston member 24.

Mounted within piston member 24 between end 26 and circular plate 32 is a coiled spring 34. In the nonactuated position of the timing device disclosed in FIG- URE l, coiled spring 34 is fully compressed and thus tends to ydrive piston member 24 toward end 14 of housing member 10.

To hold piston member 24 in the non-actuated position shown in FIGURE 1, a release pin 36 is mounted in axially aligned holes 38 and 40 in housing member 10 and piston member 24 respectively. As long as pin 36 remains in the -position shown in FIGURE l, piston member 24 cannot move from the first non-actuated position adjacent end 12 of housing member 10'.

Adjacent second end 14 of housing mem-ber 10, chamber 16 has an increased diameter portion 42. Enlarged diameter :portion 42 extends from second end 14 to a position approximately adjacent end 26 of piston member 24. Mounted within portion 42 of chamber 16 is an air-filled sack 44. In the preferred embodiment, sack 44 includes a cup-like portion 44a and a separate end cover portion 44b that are sealed together as at 46. Sack 44 is cylindrical in 'form with opposite closed ends and has a diameter corresponding to the diameter of enlarged portion 42 of chamber 16. Sack 44 is formed from a permeable material such as polyethylene film or silicone rubber. The walls of sack 44 are thin and quite flexible. The ywalls are also permeable or porous so that air can flow from chamber 16 into sack 44 or from sack 44 into chamber 16. Since the pores in the walls of sack 44 are quite small, the air iiow through the walls of sack 44 is quite slow. Under normal conditions, the air pressure within sack 44 is the same as atmospheric pressure since air will diffuse through the permeable material to equalize pressures on both sides thereof.

Although sack 44 is composed of two parts 44a and 44b in the preferred embodiment, many variations of this structure are possible. For example, section 44a could be sealed directly to end plate 20, thus eliminating section 44b. Another possibility is to substitute a metal plate 44b for the presently used permeable material. Many other variations in the design of the permeable air sack 44 will occur to those skilled in the art.

As previously stated, piston member 24 is movable from a first position adjacent end 12 to a second position adjacent end 14. To detect the movement of piston member 24 from the tirst position to the second position, a spring loaded plunger 48 is mounted in an opening S0 in housing member 1i). When piston member 24 moves to its second position, plunger 48 will be driven by its spring into chamber 16. Since plunger 48 is visible from the outside of housing member 10, its movement signals the arrival of piston member 24 at its second position.

Referring now to FIGURE 2, the timing device is shown in the actuated position with piston member 24 located in its second position adjacent second end 14. With piston member 24 in its second position, air sack 44 has been completely collapsed or deflated as shown. The air originally7 contained within sack 44 has been lfjorced through the permeable walls of sack 44 into charn- OPERATION In FIGURE 1, the timing device is shown in the nonactuated position. Piston member 24 is held in the first position, against the forces applied by coiled spring 34, by release pin 36. Sack 44 is completely filled with air at atmospheric pressure. l

To initiate the timing action, release pin 36 is removed from openings 3S and 40. l Pin 34 can be removed manually or automatically as required by the system in which the timing device is used. Immediately upon ythe removal of pin 36, coiled spring 34 begins to force piston member 24 toward second end 14 of housing member 10. The movement of piston member 24 is delayed by the controlled collapse of air sack 44. Air sack 44 collapses at a rate that is determined by the speed at which air can escape through the permeable walls. When piston member 24 reaches the second position as shown in FIGURE 2, plunger 4S is driven into chamber 16 to indicate the end of the timed period. As will be obvious to those skilled in the art, the movement of plunger 48 can be utilize-d to initiate other action within the system.

The time required for piston member 24 to move from the first position to the second position is determined by several factors. These factors include the area of end 26 acting upon sack` 44, ythe force applied by coiled spring 34, the size of air sack 44, the thickness of the walls of sack 44, and the type of material from which sack 44 is constructed. It is intended that piston member 24 should lit rather loosely in chamber 16 so that the air being forced from sack 44 can flow freely between piston member 24 and the walls of chamber 16.

In actual practice, air sack 44 has been constructed from a polyethylene iilm having a thickness of approximately .O05 inch. The polyethylene film can be formed easily into a sack as shown in FIGURE 1. The sacl will retain its shape in storage and will not collapse during storage. In the preferred embodiment, the air sack has a diameter of .375 inch and the piston member has a diameter of approximately .317 inch. Using a coiled spring that will apply 1.5 pounds pressure on the piston, the time required to completely deiiate the air sack is approximately 22 hours. That is, from the time pin 36 is removed, 22 hours are required for piston member 24 to reach the second position shown in FIGURE 2.

Silicone rubber has also been used in the air sack. The silicone rubber air sack is molded rather than formed. The silicone rubber liquid is placed in a mold and then cure-d at approximately 500 degrees to form a cup-like member such as 44a. Member 44a is then cemented to a steel plate such as 44b to form the complete air sack. Since silicone rubber is much more permeable than poly- Iethylene film, a much shorter timing period is possible. A :silicone rubber air sack having the same dimensions as those disclosed for the polyethylene film air sack above, will result in a timing period of approximately two hours.

Tests have shown that the timing period can be aC- curately controlled from unit to unit by carefully controlling the various parlms, As shown by the above examples, a Wide range of timing periods is also available. Por example, by doubling the size of all components, and at the same time using the same spring force and the same sack wall thickness, the timing period can be increased by a factor of 8. As applied to the device utilizing polyethylene lm, a timing period of approximately 176 hours would result from such changes.

From the above description, it will be apparent that I have invented a novel timing device. Although the form of the invention described herein constitutes a preferred embodiment, it will be understood that changes may be made within the spirit of the invention limited only by the scope of the appended claims. I claim as my invention:

1. A timing device, comprising:

(a) a housing member having a cylindrical chamber therein with lirst and second closed ends;

(b) a cylindrical piston member mounted in said chamber, having an -outside diameter corresponding to the inside diameter lof said Achamber and being movable between a first .position adjacent said rst end and a second position adjacent said second end;

(c) said housing member and said 4piston member each having an opening lin a side thereof, Isaid openings being aligned with said piston member in said lirst position;

(d) a -release pin mounted in said aligned openings to Ahold said pis-ton member in said first position;

(e) a spring member mounted lbetween said piston member and said iirst end to drive said piston member from said tirst posit-ion to said second position when said release pin is removed;

(t) a sealed cylindrical air-filled sack located between said piston member and said second end, .said sack having a dia-meter that is slightly lar-ger than the diameter of said piston member, said chamber having fan enlarged diameter portion adjacent said second end `to accommodate sai-d sack, ysaid sack being formed from a thin flexible permeable material that .permits the dilusion Iof air through the walls thereof so that said sack is lilled with air at a pressure corresponding to the environmental air pressure, the movement of said piston member from said` rst position to said second position being delayed by the controlled collapse of said sack as the air therein is forced through said permeable material; and

(-g) means -mounted in said housing mem-ber to detect the arrival of said piston member at said second position.

2. A timing device, comprisin:

(a) a housing member having an elongated chamber therein with lirst and second closed ends;

(-b) a piston member .mounted in said chamber having llateral dimensions corresponding 4to the lateral di- Arnensions 'of said chamber and being movable between a i-rst 4position at said first end and -a second position at said second end;

(c) a spring member mounted between said piston member and said first end to drive said piston from said iirst position to said second position;

(d) a sealed air-filled sack located in said chamber between said piston member and said second end, said lsack bein-g formed from a thin-walled flexible permeable mate-riad;

(e) means for holding said piston member in said tirst position and for releasing said piston member, the movement of said piston member trom said iirst position to said second position being delayed -by the col-lapse of .said sack as the air in said sack is forced through said permeable walils into said chamber; and

(t) means for detecting the arrival of said piston member yat said second position to measure the time delay.

3. A timing device, comprising:

(a) a tubular housing member having a bore therein with first and second closed ends;

(b) a spring loaded piston member mounted in said bore and being movable from a irst position at said rst end to .a second position at said second end under the inuence of said spring;

(c) an air-filled .sack located in said bore between said second end and said piston member; said sack being formed from a permeable material that will restrict the tiow of air therethrough;

(d) means for 4hold-ing said piston member in said Iirst position Auntil operation of the timing device is required; and

(e) means for indicating When said piston member has moved from said first position to said second position, the movement of sai-d .piston member being de- -layed by the controlled deflation of said air-lilled sack.

4. A timing device, comprising:

(a) ya housing having a closed chamber therein;

(b) an air-filled sack mounted in sai-d chamber and having walls formed from a permeable material, said sack being sealed so that air movement into and out 6 of said sack is controlled lby the permeability of said Walls;

(c) means mounted in said chamber for applying mechanical -pressure to lsaid sack to thereby deflate said sack ata rate detenmined by the applied pressure and by the restrictive effect of the dow of air through said permeable material; and

(d) means mounted in said housing for indicating when said sack is deflated.

5. A timing device, comprising:

(a) an air--lled rsack formed from `a permeable material and sealed so that air movement into yand out of said sack is controlled by the permeability of the walls of said sack;

(b) means for applying mechanical pressure to said sack to thereby deflate said sack .at a lrate determined Iby the applied pressure :and :by the Irestrictive etect of the flow of air through said permeable material; and

(c) means yfor indicating when said sack is deila-ted.

No references cited.

MILTON KAUFMAN, Primary Examiner. 

5. A TIMING DEVICE, COMPRISING: (A) AN AIR-FILLED SACK FORMED FROM A PERMEABLE MATERAIL AND SEALED SO THAT AIR MOVEMENT INTO AND OUT OF SAID SACK IS CONTROLLED BY THE PERMEABILITY OF THE WALLS OF SAID SACK; (B) MEANS FOR APPLYING MECHANICAL PRESSURE TO SAID SACK TO THEREBY DEFLATE SAID SACK AT A RATE DETERMINED BY THE APPLIED PRESSURE AND BY THE RESTRICTIVE EFFECT OF THE FLOW OF AIR THROUGH SAID PERMEABLE MATERIAL; AND (C) MEANS FOR INDICATING WHEN SAID SACK IS DEFLATED. 